1. Technical Field
This invention relates to constant velocity universal joints.
2. Related Art
Constant velocity joints are used to transmit torque through an angle while maintaining constant velocity ratio between a driving and driven shaft member of the joint at all angles. A typical constant velocity joint includes an outer member formed with a part-spherical inner surface and a series of ball grooves, an inner member formed with a part-spherical outer surface and a series of complementing ball grooves aligned with the grooves of the outer joint member, a torque-transmitting ball disposed in each groove pair, and a ball cage disposed between the inner and outer joint members and having part-spherical surfaces and contact with those of the inner and outer joint members for articulation of the joint.
The size of the joint is dependent in part on the angle to be achieved and the stack-up dimensions of the component parts, namely the inner joint part, the outer joint part and the intervening ball cage. Reducing the thickness of any one or more of these components may impair the strength or integrity of the joint, and thus there is a limit to how small a conventional constant velocity joint can be made without detracting from its strength or reducing its degree of articulation.
U.S. Pat. Nos. 5,201,107 and 5,230,659 disclose constant velocity joints in which the conventional cage is eliminated and the ball grooves of the outer joint part formed at a convergent angle toward the open end of the joint such that the walls of the grooves retain the balls from escape through the open end of the joint. An internal retainer plate or cage is disposed within the outer member axially behind the terminal end of the inner member. The retainer reacts against the outer member and the balls to keep the balls within the grooves during angulation of the joint. Both joints are of rather complex construction, requiring special machining and component parts as well as special installation techniques to assemble the parts.
It is an object of the present invention to simplify the construction and manufacture of a compact constant velocity joint.
A constant velocity joint constructed according to the invention comprises an outer joint member having at least one open end and an inner joint member disposed at least partially within the outer joint member. The outer and inner joint members have inner and outer contact surfaces which engage one another to permit relative articulation between the outer and inner joint members. The outer joint member has a plurality of circumferentially spaced grooves formed in the inner contact surface which extend axially to the open end of the outer joint member. The inner joint member has a plurality of complementary circumferentially spaced grooves formed in the outer contact surface and aligned with the grooves of the outer joint member to define facing pairs of grooves. The grooves of the joint members are of arcuate form and have centers of curvature spaced so that the grooves of each pair diverge from one another axially toward the open end of a joint member. A plurality of torque-transmitting balls are disposed one in each groove pair. A ball retainer is supported by one of the joint members axially adjacent the balls and adjacent the open end of the outer joint member in axially spaced relation to the contact surfaces of the joint members. The ball retainer confronts the balls to axially retain the balls within the groove pairs against escape through the open end of the outer joint member.
The invention further contemplates a method of fabricating a constant velocity joint in which the outer and inner joint members are formed with the contact surfaces and complementing balls grooves above. Once formed, the inner joint member is inserted at least partially into the outer joint member through the open end thereof to bring the contact surfaces of the joint members into contact with one another to provide relative articulation of the outer and inner joint members about a center and to provide associated pairs of grooves which extend to the open end of the outer joint member. Once the inner joint member is installed within the outer joint member, a torque-transmitting ball is installed in each groove pair. Following installation of the balls, a ball retainer is installed adjacent the open end of the outer joint member to retain the balls within the grooves.
The present invention has the advantage of providing a compact constant velocity joint through elimination of the standard ball cage normally present to contain the balls but adding radially thickness to the joint assembly. By eliminating the ball cage, the overall radial size of the joint is decreased. Further, the subject cage-less constant velocity joint improves upon the prior art cage-less type joints by simplifying the geometry of the contact surfaces and ball grooves and moving the ball retainer outboard of the outer member. The construction and method thus has the advantage of providing a simple, inexpensive process for manufacturing and assembling the component parts.